The present invention relates to an assembly of spinning nozzles for forming composite filaments having a core-and-sheath structure, including a nozzle plate provided with a plurality of spinning nozzles, a cover plate enclosing with the nozzle plate at least one cavity, an intermediate plate sandwiched between the nozzle and cover plates to divide the cavity into two chambers, the intermediate plate being formed with a plurality of bores arranged in alignment with respective nozzles, at least one inlet conduit communicating with a chamber between the cover plate and the intermediate plate to feed a core component therein, and at least one inlet conduit communicating with the chamber between the intermediate plate and the nozzle plate to feed a sheath component therein.
Synthetic two-component fibers or filaments having a core-and-sheath structure are manufactured in order to unite advantageous properties of different components. For example, it is possible to use as a core component a polymer of a high strength and minute expansion, and as the sheath another polymer which imparts to the filament a good dyeability or a pleasing touch. For many applications a definite filament structure is required wherein the sheath coaxially surrounds the core with a uniform thickness. This requirement can be readily fulfilled with a complex arrangement of spinning nozzles. However, in the mass production it is necessary to install large number of suitable spinning nozzles in a most restricted installation space. This requirement brings about considerable technological problems.
The German publication DE-OS No. 20 04 431 describes a pack of spinning nozzles whose nozzle plate is provided with six nozzles arranged in the corners of a regular hexagon. The intermediate plate is provided with six tubular inserts which project into the conical part of the intake funnel of respective nozzles. The axial bores of the tubular inserts are substantially in alignment with the nozzles to feed core components therein. The intermediate plate has an axial feed conduit communicating via a channel system with the inlet funnels of the nozzles to feed the sheath component therein. This prior art nozzle assembly due to its structural design is limited to a very small number of spinning nozzles which are spaced apart from one another at a relatively large distance.
The same disadvantages has a spinning nozzle assembly described in the German publication DE-OS No. 16 60 702.
Known is also from the German publication DE-OS No. 14 35 559 a spinning nozzle assembly for the production of two component filaments wherein the nozzle plate and the intermediate plate are made of relatively thin metal sheets and arranged at a minute distance one from the other. The spinning nozzles have a very large number of simple bores which are arranged closely one to each other. The interspace between the two plates communicates via bores which are distributed on the circumference of the assembly with an annular distributing channel surrounding the plate to form an inlet for one of the two components. Consequently, this component forms between the two plates a layer flowing in radial direction toward the center axis of the plates and being penetrated by thin axial streams of the other component. With this prior art pack of spinning nozzles no well-defined core-and-sheath structure of the filaments can be produced inasmuch as the interface of the two components in respective filaments is non-uniform and irregular.
Another spinning nozzle assembly having a large number of spinning nozzles arranged closely one to each other is disclosed in the European Pat. No. EP-A2-0 128 013. In this pack of spinning nozzles two separate, interleaved channel systems each consisting of a plurality of grooves, are provided on the upper surface of the intermediate plate. Each of the grooves has on its bottom a series of throughbores so that a system of throughbores is assigned to a corresponding channel system. The throughbores of one channel system are aligned with the spinning nozzles and serve for feeding the core component. The throughbores of the other channel system are arranged such that each throughbore of the first channel system is surrounded by a plurality of throughbores of the other channel system. A third plate provided with bores serves for connecting one of the channel systems of the intermediate plate with a supply chamber 4 for the core component and the other channel system with a supply chamber for the sheath component. It is true that in this prior art spinning nozzle assembly the inflow conditions for all nozzles are the same, nevertheless the particular feeding of the sheath component does not guarantee any exact concentric structure of the excluded filament. Moreover, the structural height of the nozzle assembly due to the additional third plate is relatively large.